Need help with errors

**yaya** · 05-25-2007

I'm trying to make a simple text RPG with Dev C++ that has spells as a form of attack. Anyways, I have a class for the spells in a .h file but it comes up with errors saying:

"'std::string spell::name is private' within this context"

I'm relatively new to classes and this makes next to no sense to me. This is the code its coming up with errors on:

Code:

class spell
{
      private:
              string name; //spell name
              int damage; //damage
              bool fire; //element
};

inline void load()
{
              spell fire1;
              fire1.name=("Inferno");
              fire1.damage=1;
              fire1.fire=true;
}

Thanks in advanced.

**laserlight** · 05-25-2007

Free functions cannot access non-public members of a class unless they are friends of the class. It looks like you may want to provide a constructor for your class and use that.

**yaya** · 05-25-2007

Alright, so I added the constructor & destructor (I'm not great with these either) but now I get a new error saying:

"[Linker Error] undefined reference to 'spell::~spell()'"

Code:

class spell
{
      public:
              spell();
              ~spell();
      private:
              string name; //spell name
              int damage; //damage
              bool fire; //element
};

spell::spell()
{
              spell fire1;
              fire1.name=("Inferno");
              fire1.damage=1;
              fire1.fire=true;
}

spell::~spell()
{
}

What am I doing wrong this time?

**AverageSoftware** · 05-25-2007

Remove spell fire1; from the constructor. Your constructor is building another spell object, which will build another spell object, which will build another... and so on.

Your constructor should look like this:

Code:

spell::spell()
{
              name=("Inferno");
              damage=1;
              fire=true;
}

**yaya** · 05-25-2007

I see. Thanks a bunch, all.

**Daved** · 05-25-2007

You should really be using the initializer list in your constructors to initialize the variables like this:

Code:

spell::spell() : name("Inferno"),  damage(1), fire(true)
{
}

**yaya** · 05-25-2007

Alright, I have no idea what to do. I'll just give you the entire .h file with all the spells and stuff because I'm still getting the same linker error.

**Richie T** · 05-26-2007

There's a couple of problems with this. Firstly, exactly what laserlight said - the variables in the class are declared as private - this means that only member functions of the class or friend functions can access them. 'load' is not a member function or friend function, so that's where the error comes from. To fix it you would probably do something like this:

Code:

class spell
{
public:
     spell();
     ~spell();
     void load (parameters);	// this is how to declare a member function
     // or use
     void friend load (parameters)	// this is declaring the global function as a friend

private:
      string name;
      int damage;
  		//catagories
      bool fire;
	  // etc.
};

// Then you'd do this

void spell::load(parameters)	// if using the member method
{
	// Code
}

// or

void load (parameters)	// if using the friend approach
{
	// Code
}

Secondly, I notice that you declare a number of instances of spells in 'load', which is perfectly allowed - it looks like you want to use the function to declare and setup all the variables. The problem is that it's probably a bit useless in your program because of scope - if you write a function and declare variables in it, that data can't be accessed from other functions unless you return a value from the function. What you can do is declare variables the calling function (eg if you are in main and are calling load, main is the calling function) and pass them by pointer/reference to load if using the friend approach, or just us the member function approach and call the method - much easier for this type of thing:

Code:

// headers and stuff

// Load is a member of spell

int main (void)
{
	spell var1, var2;	// etc;

	// Code that determines the values to use (eg read in from user)

	var1.load(values);
	var2.load(values);	// etc

	return 0;
}

This is essentially the same idea as using a constructor - in fact a constructor is the preferred method for this since declaration and initialisation occur in a nice single statement.

Lasty, you probably don't need to use inline...

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